Many gas wells produce liquids in addition to gas. These liquids include water, oil, and condensate. As described in the paper SPE 2198 of the Society of Petroleum Engineers of AIME, authored by R. G. Turner, A. E. Dukler, and M. G. Hubbard, “in many instances, gas phase hydrocarbons produced from underground reservoirs will have liquid-phase material associated with them, the presence of which can effect the flowing characteristics of the well. Liquids can come from condensation of hydrocarbon gas (condensate) or from interstitial water in the reservoir matrix. In either case, the higher density liquid phase, being essentially discontinuous, must be transported to the surface by the gas. In the event the gas phase does not provide sufficient transport energy to lift the liquids out of the well, the liquid will accumulate in the well bore. The accumulation of the liquid will impose an additional back pressure on the formation and can significantly affect the production capacity of the well”. Over time, accumulated liquid can cause a complete blockage and provoke premature abandonment of the well. Removal of such liquid restores the flow of gas and improves utilization and productivity of a gas well.
There are many technical solutions that have been suggested in the prior art to solve the problem of accumulating liquids. Some of them are described briefly by E. J. Hutlas and W. R. Granberry in the article entitled “A Practical Approach to Removing Gas Well Liquids” in the Journal of Petroleum Technology, August 1972, p. 916–922. Others are summarized in the U.S. Pat. No. 5,904,209. More recent advances in operating gas and other hydrocarbon wells are found for example in the U.S. Pat. Nos. 5,636,693; 5,937,946; 5,957,199 and 6,059,040.
Submersible pumps may also be used to overcome the above-described problem. However the costs of deploying such pumps are often not justified for low margin gas wells
On the other hand, it is known that production from low pressure reservoirs can be enhanced by jet pumps and artificial lift operations. For instance, hydraulic jet pumps have been used as a down hole pump for artificial gas lift applications. In these types of hydraulic pumps, the pumping action is achieved through energy transfer between two moving streams of fluid. The power fluid at high pressure (low velocity) is converted to a low pressure (high velocity) jet by a nozzle or throat section in the flow path of the power fluid. The pressure at the throat becomes lower as the power fluid flow rate is increased, which is known as the Venturi effect. When this pressure becomes lower than the pressure in the suction passageway, fluid is drawn in from the well bore. The suction fluid becomes entrained with the high velocity jet and the pumping action then begins. After mixing in the throat, the combined power fluid and suction fluid is pumped to the surface.
In the light of the above background it is an object of the present invention to provide effective and economically viable methods and apparatus for cleaning gas wells.